The present invention relates generally to a system and method for controlling a conveyor system to accommodate differently sized substrates. More specifically, the present invention relates to a system and method for adjusting conveyor rails of a conveyor system in a dispensing system to accommodate differently sized substrates.
There are several types of prior art dispensing systems used for dispensing metered amounts of liquid or paste for a variety of applications. One such application is in the assembly of printed circuit boards and integrated circuit chips. In this application, dispensing systems are used in the process of encapsulating integrated circuits with an encapsulating material and in the process of underfilling flip integrated circuit chips with an encapsulant. Prior art dispensing systems are also used for dispensing dots or balls of liquid epoxy or solder paste onto circuit boards and integrated circuits. The liquid epoxy and solder is used to connect components to a circuit board or to an integrated circuit. The dispensing systems described above include those manufactured and distributed by Speedline Technologies, Inc., assignee of the present invention, under the name CAMALOT(trademark).
The dispensing systems described above are typically used in an electronics manufacturing facility in an automated assembly line with other equipment used in a circuit board or integrated circuit manufacturing process. The other equipment in-line with the dispensing systems may include, for example, pick and place machines, which place components on circuit boards, or reflow ovens that are used to cure materials dispensed onto the circuit boards or integrated circuits.
In a typical dispensing system, a pump and dispenser assembly is mounted to a moving assembly for moving the pump and dispenser assembly along three mutually orthogonal axes (x, y, z) using servomotors controlled by a computer system or controller. To dispense a dot of liquid on a circuit board at a desired location, the pump and dispenser assembly is moved along the horizontal x and y axes until it is located over the desired location. The pump and dispenser assembly is then lowered along the vertical z axis until the nozzle of the pump and dispenser assembly is at an appropriate dispensing height over the board. The pump and dispenser assembly dispenses a dot of liquid, is then raised along the z axis, moved along the x and y axes to a new location, and is lowered along the z axis to dispense the next liquid dot.
During the manufacture of circuit boards, a conveyor system is typically employed to transport the circuit boards through several processing stations associated with the dispensing system. It is sometimes necessary, or desirable, to process differently sized circuit boards. As a result, spacing between conveyor rails of the conveyor system requires adjustment. Typically, an operator of the dispensing system is required to physically move the conveyor rails to adjust the spacing of the rails to accommodate the differently sized circuit board. In this arrangement, the operator is required to re-adjust the spacing of the conveyor rails each time a differently sized circuit board is transported on the conveyor rails of the conveyor system.
One deficiency with requiring an operator to re-adjust the conveyor rails of the conveyor system, as described above, relates to reduced output of the circuit board manufacturing process. In particular, the circuit board manufacturing process needs to be stopped for a period of time to enable the operator to re-adjust the spacing of the conveyor rails. Stopping the circuit board manufacturing process for a period of time significantly reduces volume production and adds significant costs to the final products produced. Another deficiency of this re-adjustment requirement is related to operator error. If the operator fails to precisely space the rails of the conveyor system, the circuit boards can either fall off of the conveyor system (e.g. rails spaced to far apart) or the circuit boards can become jammed in other machinery associated with the conveyor system (e.g. rails spaced to close together).
Some conveyor systems include motorized rails for reducing operator intervention during the process of re-adjusting rails of the conveyor system. In this type of conveyor system, for example, a motor is coupled to at least a first rail of the conveyor system. The motor is used to move the first rail relative to an adjacently positioned second rail to adjust a space between the first rail and the second rail to accommodate different size circuit boards. In operation of this conveyor system, the motor is initially controlled to move the first rail to a reference position. The motor is thereafter controlled to move the first rail from the reference position to a position for carrying the circuit boards, which is a predetermined distance from the reference position. The predetermined distance for which the first rail is moved is typically measured by an encoder that is coupled to the motor.
One deficiency with this type of conveyor system relates to the time required to initialize the position of the first rail during system start-up, after a power loss or after a system reset. Other deficiencies with this type of conveyor system can occur if the conveyor system includes multiple conveyor lanes. The multiple lane conveyor system can include a plurality of pairs of rails, for which some or all of the rails may require initial positioning at the reference position, as previously described. Further, during the course of operations using the multiple lane conveyor system it may become necessary to re-adjust fewer than all of the lane widths, which would require fewer than all of the motorized rails to return to the reference position and then move to an operating position.
One deficiency occurs in that adjacent lanes that do not require lane re-adjustment may be positioned intermediate the lane that requires re-adjustment and the reference position, thus blocking the motorized rail from moving to the reference position without disturbing the operating position of the adjacent lanes that do not require lane re-adjustment.
Therefore, a need exists for a control system and method for controlling a conveyor system to precisely adjust conveyor rails of the conveyor system to accommodate differently sized substrates, which overcomes the deficiencies and limitations described above.
Embodiments of the present invention provide a control system and method for controlling a conveyor system configuration to precisely adjust conveyor rails of the conveyor system to accommodate differently sized substrates.
In accordance with one aspect of the present invention, an apparatus for performing a task on a work piece is provided. The apparatus includes an object that performs the task on the workpiece, a work surface, a conveyor system mounted on the work surface and having at least a first rail and at least a second rail separated by a first space equal to a first conveyor lane width value, a support structure coupled to the work surface, the support structure being coupled to the object to support the object over the conveyor system, at least one camera mounted on the support structure, and a processor coupled to the at least one camera. The at least one camera is constructed and arranged to capture a first image of a first registration mark associated with the first rail and to capture a second image of a second registration mark associated with the second rail and to provide the first and second images to the processor. Further, the processor is programmed to receive the first and second images and determine the first conveyor lane width value.
The conveyor system can further include at least a third rail and at least a fourth rail separated by a second space equal to a second conveyor lane width value. The at least one camera can be constructed and arranged to capture a third image of a third registration mark associated with the third rail and to capture a fourth image of a fourth registration mark associated with the fourth rail and to provide the third and fourth images to the processor to determine the second conveyor lane width value. The first registration mark can be located at a first predetermined position on the first rail and the second registration mark can be located at a second predetermined position on the second rail. The apparatus can further include a motor coupled to the processor and to the first rail, the motor being adapted to receive and respond to control signals provided by the processor to move the first rail a distance based on a first conveyor lane adjustment value generated by the processor. The apparatus can further include at least one gantry system having a slidably mounted platform adapted to securely hold the object and to move the object over work pieces on the conveyor system. The platform can be further adapted to securely hold the at least one camera and to move the at least one camera over the conveyor system. The object can include a material dispensing head.
Another aspect of the present invention is directed to a method of controlling a conveyor system configuration, having a first rail and a second rail, to accommodate a plurality of differently sized substrates. The method includes positioning a camera to capture at least one image of the conveyor system, determining a distance between the first rail and the second rail based at least in part on the at least one image, comparing the distance determined with a desired distance, and moving at least one of the first rail and the second rail to set the distance substantially equal to the desired distance.
The method can include positioning a camera to a first position over the first rail to capture an image of the first rail, and positioning the camera to a second position over the second rail to capture an image of the second rail. The step of determining a distance can include determining a distance between the first position and the second position.
Another aspect of the present invention is directed to an apparatus that positions an object to perform a task on a work piece. The apparatus includes the object, a work surface, a support structure positioned over the work surface and constructed and arranged to support the object over the work surface, a conveyor system mounted on the work surface and having at least a first rail and at least a second rail separated by a first space equal to a conveyor lane width, and means for viewing the conveyor system and for determining the conveyor lane width.
The apparatus can further include means for moving at least one of the first rail and the second rail to adjust the conveyor lane width. The means for viewing the conveyor system and for determining the conveyor lane width can include a camera and means for moving the camera to a first position over the first rail and to a second position over the second rail. The means for viewing the conveyor system and for determining the conveyor lane width can include means for determining a distance between the first position and the second position.